Lockheed Martin has completed final assembly of NASA's Origins, Spectral Interpretation, Resource Identification, Security, Regolith EXplorer (OSIRIS-REx) deep-space probe. The unmanned spacecraft, designed to rendezvous with an asteroid and return samples to Earth, will now undergo five months of environmental testing at the company’s Space Systems facilities near Denver before delivery to the Kennedy Space Center in Florida.

Scheduled for launch in September 2016, OSIRIS-REx is designed to rendezvous with the near-Earth asteroid Bennu in 2018. Bennu is one of only five B-type asteroids that is of suitable size and orbit for rendezvous and sample return. It’s also one of the most likely asteroids to hit Earth in the next few centuries, so taking a close look has an element of self-interest. Another point of interest is that it's a carbonaceous asteroid that may provide insights into the origins of the Solar System as well as the source of water and organic molecules on Earth.

Once it reaches Bennu, OSIRIS-REx will spend a year examining the asteroid, including a detailed study of its chemistry, mineralogy and topography. It will also compare telescope-based data with on-the-spot observations and make a precise determination of the asteroid’s orbit. It will then touch the asteroid with a telescopic probe, which will use a blast of compressed nitrogen gas to blow a 2-oz (60 g) dust sample into a collection filter before returning to Earth in 2023. The sample will make a landing using a Sample Return Capsule of the same design as that used for returning comet samples on previous missions.

According to Lockheed, OSIRIS-REx will spend the next five months going through an intense battery of tests to determine its suitability for deep space. It will be subjected to electromagnetic radiation, hard vacuum, extreme heat and cold, vibrations and separation and deployment shock similar to that it will experience during launch. If all goes well, it will then ship to Kennedy in May for final launch preparations.

"This milestone marks the end of the design and assembly stage," says Dante Lauretta, principal investigator for OSIRIS-REx at the University of Arizona, Tucson. "We now move on to test the entire flight system over the range of environmental conditions that will be experienced on the journey to Bennu and back. This phase is critical to mission success, and I am confident that we have built the right system for the job."